What’s new in Total Hip Replacement?
Dec 14, 2017
As most people would be aware Hips are the second most replaced joint, and most often for Osteoarthritis. Other conditions such as developmental disorders and Sero-positive arthritis are diminishing with better detection and medical treatment.
The numbers of hip replacements are steadily increasing at 2% per annum. The rate of hip replacement increased between 2004 and 2014 from 83 to 104 per 100,000 population. The results, also are steadily improving, with survivorship of 90% at 15 years, National Joint Replacement Registry. I think it is fair to say, that if you have a well-functioning hip at 12 months, it should be the same at 20 years. This is largely down to improved bearing surfaces of ceramic and last generation hard plastics, both of which show minimal wear at 15 years.
The trend towards less invasive surgery has had a few false starts over the last 20 years. Initially the emphasis was on small incisions but now we are hoping to achieve minimal tissue trauma, by operating between tissue planes, rather than by detaching muscles. There are several techniques which achieve this goal. The Anterior Technique has been popular in Europe for the last 20 years and has been refined over that period, to be reproducible and create minimal trauma. Several variations exist but all have been associated with a more rapid recovery when compared with traditional techniques. These techniques report less pain, quicker mobilisation, lower incidence of dislocation, less blood loss and subsequent need for transfusion.
This is not the whole story, because throughout the last decade the introduction of better pain management protocols, patient education programs, more rigid transfusion protocols and the use Tranexamic acid and fibrin sealants have helped reduce bruising, pain and aided early rehabilitation.
Recently, the goal has been to accurately re-establish the 3D spatial orientation of the joint.
This involves multiple techniques, including computerised preoperative templating, intra-operative devices for re-establishing leg length and hip offset and intra-operative imaging.
There are patient specific guides generated from computer models which can accurately cut the bones, and recently there has been the introduction of robotics. The latter is still in an early stage of utility, being expensive, awkward and time consuming to use. No doubt with development it will become more user friendly, much as computer navigation in the knee has become over the last 15 years. It is now possible in the non-dysplastic arthritic hip to achieve an accuracy within 5mm for leg length, femoral offset and hip centre of rotation. The impact this has on function is still being evaluated but intuitively, one would expect function closer to the native hip.
The next evolution of improving functionality has been to assess not only the anatomic orientation of the hip but the functional orientation. As we age, we lose flexibility in our spine, which most often manifests as a loss of lordosis, which means the acetabulum, goes from being perpendicular to the ground, when we stand, to being more anteriorly orientated. This coupled with spinal surgery, scoliosis and leg length disorders alter the mechanical alignment of the hip and increase the risk of impingement, dislocation and abnormal wear. Radiological techniques are available to do functional assessments of the hip and suggest better orientation of the prosthetic components.
What I find very encouraging about all these developments, is that I am seeing an increasing number of people returning to work by 6 weeks, and returning for review at 12 months with no symptoms, a normal range of motion and gait. We have not solved every problem yet, but compared to hip replacement 20 years ago we have seen a transition from hoping to minimise pain, having variable success with functionality and resignation to eventual failure, to a potential for no pain, a normal gait and excellent survivorship.
Dr John Ireland
Suite 701, Level 7
Wollongong Private Hospital
360-364 Crown St
Wollongong NSW 2500
P: 02 9821 2599